Effect of microstructure evolution on tensile fracture behavior of Mg-2Zn-1Nd-0.6Zr alloy for biomedical applications

The effect of microstructure evolution on tensile fracture behavior of biomedical Mg-2Zn-1Nd-0.6Zr alloy was investigated using OM, EPMA, SEM, TEM, EBSD and Nano-indentation. Results indicated that the as-cast Mg-2Zn-1Nd-0.6Zr alloy composed of alpha-Mg matrix, netlike and granular Mg35Zn40Nd25 (T-3) secondary phases. Volume fraction of secondary phases in homogenized and solution-treated alloys decreased from 72% to 4.6% and 0%, respectively, whilst elements distributed more uniform and grain did not grow significantly. Grain size of extruded + aged alloy decreased from 110 mu m to 12 mu m, forming band-shaped phases with size of 02-1.5 mu m and high-density nanoscale precipitates with size of 5-20 nm. Moreover, Mg35Zn40Nd25 phase exhibited higher elastic modulus ( 57.5 GPa) and hardness (1.47 GPa) than all matrices. With the change of phase content, phase morphology and grain size, the fracture mode of as-cast, homogenized, solution-treated and extruded + aged alloys during the conventional tensile test changed from intergranular fracture to quasi-cleavage fracture, transgranular fracture and ductile fracture. In addition, the effect of reduced surface integrity on cracking susceptibility could be ranked in the order of as-cast > homogenized > solution-treated > extruded + aged. (C) 2019 The Authors. Published by Elsevier Ltd.